As disclosed in U.S. Pat. No. 3,506,556 (Apr. 14, 1970--Gillery et al), the deposition of metals and metal-oxide films by cathodic sputtering is a well-known process. The text "Vacuum Deposition of Thin Films", by Holland, Published by Chapman and Hall, Ltd., London, (1963) is referred to and discusses the technology of cathodic sputtering.
In cathodic sputtering processes, an atmosphere at greatly-reduced pressure is necessary to provide the proper conditions for a glow discharge to occur between cathode and anode. A glow discharge energizes ions present between the cathode and anode. Pyrolyzation is another technique for depositing metal oxide films on a substrate and comprises contacting the heated substrate with a metal salt or organo-metallic compound which pyrolyzes at the temperature of the substrate to form thereon an adherent metal oxide film. This technique has disadvantages but metal oxide films regardless of the method of application, have one disadvantage in comparison with metal films: low conductivity.
One method of improving the conductivity of metal oxide film has been to "dope" with another metal, preferably one of a higher valence.
U.S. Pat. No. 3,506,556 is concerned with producing conductive metal oxide films by cathodic sputtering. It is particularly concerned with cathodic sputtering from a metal having an atomic number between 48 and 51, particularly indium in an atmosphere containing hydrogen and oxygen.